/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.server.handler;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.http.HttpStatus;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.lang.Nullable;
import org.springframework.web.server.ResponseStatusException;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.WebExceptionHandler;
import reactor.core.publisher.Mono;

/**
 * Handle {@link ResponseStatusException} by setting the response status.
 *
 * <p>By default exception stack traces are not shown for successfully resolved
 * exceptions. Use {@link #setWarnLogCategory(String)} to enable logging with
 * stack traces.
 *
 * @author Rossen Stoyanchev
 * @author Sebastien Deleuze
 * @since 5.0
 */
public class ResponseStatusExceptionHandler implements WebExceptionHandler {

    private static final Log logger = LogFactory.getLog(ResponseStatusExceptionHandler.class);


    @Nullable
    private Log warnLogger;


    /**
     * Set the log category for warn logging.
     * <p>Default is no warn logging. Specify this setting to activate warn
     * logging into a specific category.
     *
     * @see org.apache.commons.logging.LogFactory#getLog(String)
     * @see java.util.logging.Logger#getLogger(String)
     * @since 5.1
     */
    public void setWarnLogCategory(String loggerName) {
        this.warnLogger = LogFactory.getLog(loggerName);
    }


    @Override
    public Mono<Void> handle(ServerWebExchange exchange, Throwable ex) {
        if (!updateResponse(exchange.getResponse(), ex)) {
            return Mono.error(ex);
        }

        // Mirrors AbstractHandlerExceptionResolver in spring-webmvc...
        String logPrefix = exchange.getLogPrefix();
        if (this.warnLogger != null && this.warnLogger.isWarnEnabled()) {
            this.warnLogger.warn(logPrefix + formatError(ex, exchange.getRequest()), ex);
        }
        else if (logger.isDebugEnabled()) {
            logger.debug(logPrefix + formatError(ex, exchange.getRequest()));
        }

        return exchange.getResponse().setComplete();
    }


    private String formatError(Throwable ex, ServerHttpRequest request) {
        String reason = ex.getClass().getSimpleName() + ": " + ex.getMessage();
        String path = request.getURI().getRawPath();
        return "Resolved [" + reason + "] for HTTP " + request.getMethod() + " " + path;
    }

    private boolean updateResponse(ServerHttpResponse response, Throwable ex) {
        boolean result = false;
        HttpStatus status = determineStatus(ex);
        if (status != null) {
            if (response.setStatusCode(status)) {
                if (ex instanceof ResponseStatusException) {
                    ((ResponseStatusException) ex).getHeaders()
                            .forEach((name, value) -> response.getHeaders().add(name, value));
                }
                result = true;
            }
        }
        else {
            Throwable cause = ex.getCause();
            if (cause != null) {
                result = updateResponse(response, cause);
            }
        }
        return result;
    }

    /**
     * Determine the HTTP status implied by the given exception.
     *
     * @param ex the exception to introspect
     * @return the associated HTTP status, if any
     * @since 5.0.5
     */
    @Nullable
    protected HttpStatus determineStatus(Throwable ex) {
        if (ex instanceof ResponseStatusException) {
            return ((ResponseStatusException) ex).getStatus();
        }
        return null;
    }

}
